Wolfenstein, DOOM and similar games relied on a technique called "raycasting." You can read about it here
, as well as some see Java code
This is a very complex way of rendering a simple-looking 3D scene. It gets much more complex when you start adding lighting, textures, collisions, etc. Since performance is crucial here, things like PBOs, shaders, proper texture storage, etc. will be things you may consider; Slick never intended to support this kind of work so it likely won't play well with your low-level OpenGL calls.
All in all, it's a pretty absurd undertaking for somebody new to graphics/3D/OpenGL programming. Instead, I'd suggest: (a) learn to program a 3D game in OpenGL or use a high-level wrapper like Ardor3D/jME, or (b) make an isometric game; it will be much easier to fake 2.5D graphics and it will still allow you to use Slick.